One the most common mistakes that many Webmasters and SEOs make is that they misuse the robots.txt, the META-robots and the rel=nofollow. All the above affect the indexing, the crawling and the PageRank distribution and as a result they can heavily affect the SEO status of a website and its rankings. In this article we will see what is their impact on SEO and how you should use them to improve the rankings of your website.